In accordance with a development of lightening and thinning LCDs, an amount of light emitting diodes (LEDs) required for backlight is reduced.
Referring to FIG. 1, in a side-light type backlight module, the amount of the LEDs is reduced, resulting in an increase of a distance P′ between the LEDs. Since a density of a light guide plate 12′ is different to a density of air, normally less than the density of air, a refraction of light rays arises when the light rays are emitted from the LEDs 11′ into the light guide plate 12′.
When the light rays are emitted form the LEDs 11′, a portion of the light rays is normally incident to the light guide plate 12′, and the normally incident light rays have an angle θair of 90 degrees. When entering the light guide plate 12′, the light rays have a reflection angle θLGP=arcsin(1/nLGP), and angle θLGP is less than 90 degrees.
Concerning the normally incident light, when a light mixing distance d is constant, and the angle θLGP is reduced, the light rays will be only distributed in specific regions of the light guide plate 12′, resulting in a hotspot problem of an uneven brightness distribution.
As a result, it is necessary to provide a backlight module and a liquid crystal display apparatus to solve the problems existing in the conventional technologies, as described above.